<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <meta name="keywords" content="这里写网页的关键字">
    <meta name="description" content="这是网页的简介">
    <style type="text/css">
        *{
            margin: 0;
            padding: 0;
            border: 0;
        }
        .main{
            margin: 16px;
            padding: 100px;
            height: 100px;
            /*
            border-style:solid;
            border-width:2px 4px 8px 16px;
            border-color:#0000FF #00FF00 #01AAED #eb7350;
            */
            border-top: 2px solid #1E9FFF;
            /*            上    右   下   左*/
        }
    </style>
</head>
<body>
<div class="main">
    123456
</div>
</body>
</html>